TY - GEN A1 - Dreibati, Ossama A1 - Ossenbrink, Ralf A1 - Doynov, Nikolay A1 - Michailov, Vesselin T1 - Physical and numerical simulation of thermo-mechanical properties in the weld heat affected zone of an AlMgSi-alloy T2 - Materials Science Forum Y1 - 2012 SN - 0255-5476 VL - 706-709 SP - 1491 EP - 1496 ER - TY - GEN A1 - Genchev, Gancho Vladimirov A1 - Dreibati, Ossama A1 - Ossenbrink, Ralf A1 - Doynov, Nikolay A1 - Michailov, Vesselin T1 - Physical and Numerical Simulation of the Heat-affected Zone of Multi-pass Welds T2 - Materials Science Forum N2 - The paper presents a numerical and experimental approach for the quantification of the thermo-mechanical properties in multi-pass weld’s heat affected zone (HAZ) of low alloy steel “S355J2+N”. First, the characteristic temperature cycles for multi-pass welds were identified by FE temperature field simulations of welding. Based on the identified temperature cycles, the microstructure in the HAZ has been physically simulated with the simulation and testing system Gleeble 3500 to investigate the influence of multi thermal exposure on the thermo-mechanical properties. Thus, the thermo-mechanical material properties including thermal strain and temperature dependent stress strain behaviour as function of peak temperatures and cooling rates have been determined. These material properties were used to calibrate a developed model for numerical prediction of the material properties of multi-pass weld HAZ. KW - welding simulation KW - multi-pass welds KW - thermo-mechanical properties KW - physical simulation, Gleeble Y1 - 2013 UR - www.scientific.net/MSF.762.544 SN - 0255-5476 IS - Vol. 762 SP - 544 EP - 550 ER - TY - GEN A1 - Zhang, Wei A1 - Doynov, Nikolay A1 - Wolf, Matthias A1 - Dreibati, Ossama A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Investigation of the Thermal Shock Behavior of Ceramic Using a Combination of Experimental Testing and FE-Simulation Methods T2 - Advanced engineering materials N2 - Thermal shock behavior of ceramics plays a decisive role in their broad industrial applications. For enhanced understanding of damage and failure mechanism under thermal shock loading, in the present work, a combination of experimental testing and numerical simulation methods has been used. The thermal shock behavior of the alumina (99.7%) disk samples has been investigated by using a plasma test stand: the bottom of the ceramic disks were locally heated in the center by plasma beam; during the heat treatment the temperature distribution at the top of the sample was recorded with a thermographic system. To characterize the thermal shock resistance, a thermomechanical simulation was subsequently carried out. It calculates the temperature and stress distribution within the ceramic disks. The calculated critical thermal tension stresses are reported, which led to the failure of the ceramic disks under thermal shock loading. The effect of the sample thickness on the temperature and stress distribution is presented. Compared with the experimental results the simulated results show excellent agreement. As conclusion, it is possible to determine the thermal shock behavior of ceramic materials by the combination of experimental testing and numerical simulation. KW - Thermal Shock Behavior KW - Ceramic KW - FE-Simulation KW - Experimental Testing Y1 - 2013 UR - http://www.aem-journal.com U6 - https://doi.org/10.1002/adem.201200241 SN - 1527-2648 VL - 15 IS - 6 SP - 480 EP - 484 ER - TY - GEN A1 - Dreibati, Ossama A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Quantification of cold cracking parameters of high strength steels by physical simulation under welding conditions T2 - Quarterly journal of the Japan Welding Society N2 - Cold cracks in welds are the result of the formation of brittle microstructure as martensite in the presence of diffusible hydrogen as well as of tensile stresses. Cold cracks occur when the combination of cold crack influence parameters (CCIP) overcomes a critical limit. In this study, critical combinations of CCIP were identified with an enhanced test procedure under welding conditions. The test is based on the physical simulation technique of heat affected zone (HAZ) and it is carried out using the test and simulation center Gleeble 3500. Thereby, laboratory special specimens are charged with hydrogen from pure hydrogen atmosphere in the initial stage of the test. Rigidly restraint specimen section is subjected to different weld temperature cycles. Through the thermal exposure, the desired microstructure of HAZ is set in the test zone of the restraint specimen section. A plastic deformation takes place owing to the prevented expansion during heating and contraction of the specimen during cooling. Consequently, compressive or tensile reactions stresses arise in the deformed zone. Cracked specimen represents a critical combination of the CCIP. The quantitative cold crack criterion separates the cold crack susceptible combinations from those non susceptible. KW - Cold Cracking KW - Physical Simulation KW - High Strength Steel Y1 - 2013 U6 - https://doi.org/10.2207/qjjws.31.148s SN - 0288-4771 VL - 31 IS - 4 SP - 148 EP - 152 ER - TY - GEN A1 - Michailov, Vesselin A1 - Dreibati, Ossama A1 - Ossenbrink, Ralf A1 - Schweizer, Frank T1 - Rechnergestützte Vorhersage der Kaltrissneigung laserstrahlgeschweißter Bauteile aus hochfesten Stählen - Teil 1 T2 - Schweißen und Schneiden : Fachzeitschrift für Schweißen und verwandte Verfahren KW - Kaltriss KW - hochfeste Stähle KW - laserstrahlgeschweißte Bauteile Y1 - 2013 SN - 0036-7184 VL - 65 IS - 11 SP - 776 EP - 781 ER - TY - GEN A1 - Atanga, Valetine Kubong A1 - Zhang, Wei A1 - Dreibati, Ossama A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin A1 - Scheffler, Michael T1 - Alumina-mullite Materials for Refractory Applications: Microstructure, Physical and Finite Element Simulation of Thermal Shock Behaviour T2 - refractories WORLDFORUM Y1 - 2012 SN - 1868-2405 VL - 4 IS - 1 SP - 159 EP - 164 ER - TY - CHAP A1 - Dreibati, Ossama A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Hydrogen charging of high strength steel specimens and physical simulation of cold cracking under laser beam welding conditions T2 - THERMEC 2011, International Conference on Processing & Manufacturing of Advanced Materials, processing, fabrication, properties, applications, August 1 - 5, 2011, Quebec City, Canada, Vol. 2 Y1 - 2012 SN - 978-3-0-3785-303-0 SP - 1391 EP - 1396 PB - TTP, Trans Tech Publ. CY - Durnten-Zurich [u.a.] ER - TY - CHAP A1 - Dreibati, Ossama A1 - Ossenbrink, Ralf A1 - Doynov, Nikolay A1 - Michailov, Vesselin T1 - Physical and numerical simulation of thermo-mechanical properties in the weld heat affected zone of an AlMgSi-alloy T2 - THERMEC 2011, International Conference on Processing & Manufacturing of Advanced Materials, processing, fabrication, properties, applications, August 1 - 5, 2011, Quebec City, Canada, Vol. 2 Y1 - 2011 SP - 1491 EP - 1496 PB - TTP, Trans Tech Publ. CY - Durnten-Zurich [u.a.] ER - TY - CHAP A1 - Dreibati, Ossama A1 - Zhang, Wei A1 - Wolf, Matthias A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Thermo-mechanical properties of refractory ceramic for the numerical simulation of their thermo-shock behaviour Y1 - 2011 ER - TY - THES A1 - Dreibati, Ossama T1 - Physical welding simulation of the cold crack susceptibility KW - Cold Crack; hydrogen embrittlement; Cold crack criterion; High strength steel Y1 - 2014 SN - 978-3-8440-3133-1 PB - Shaker CY - Aachen ER -